Re: Question on 'SQL' tracing

On Mon, May 12, 2008 at 05:15:34PM +0100, Martin Evans wrote:
> Martin Evans wrote:
>> After seeing the recent posting by Greg Sabino Mullane in subject "Log DBI 
>> query and values with placeholders" I realised there was something else 
>> DBD::ODBC was out of date with - tracing.
>>
>> DBD::ODBC does not implement its own trace flags but neither does it react 
>> to 'SQL' tracing. If I set trace('SQL') I can see the TraceLevel is set to 
>> 256 and I can find:
>>
>>     sub parse_trace_flag {
>>         my ($h, $name) = @_;
>>         #      0xddDDDDrL (driver, DBI, reserved, Level)
>>         return 0x00000100 if $name eq 'SQL';
>>         return;
>>     }
>>
>> in DBI. So to test if 'SQL' is enabled we:
>>
>> if *DBIc_TRACE_LEVEL(imp_xxh) & 256) {blah;}
>
> and also, how do I set this in Perl:
>
> $dbh->{TraceLevel} = 'SQL|3';
>
>     DBI::db=HASH(0x82ba9d4) trace level set to 0x100/3 (DBI @ 0x0/0) in DBI 
> 1.601-ithread (pid 4574)
>
> $dbh->prepare(xxxx)
>   here when I examine DBIc_TRACE_LEVEL(imp_dbh) it is 3!
>
> Similarly if I use:
>
> $h->trace($h->parse_trace_flags('SQL'))
>
> What am I doing wrong? I'm a little confused by this since DBD::Pg seems to 
> expect 'SQL' to work.

I presume you've read http://search.cpan.org/~timb/DBI/DBI.pm#TRACING

What's missing is an equivalent section in the DBI::DBD docs.
At the moment there's just a passing mention at the end of an unrelated section:
http://search.cpan.org/~timb/DBI/lib/DBI/DBD.pm#The_dbd_drv_error_method

The short answer is that DBIc_TRACE_LEVEL only gives you the 'trace
level' not the 'trace flags' (which you can get via DBIc_TRACE_FLAGS).

You probably want to use the fancy DBIc_TRACE macros though...

Hopefully this chunk of DBIXS.h with help:

#define DBIc_TRACE_LEVEL_MASK   0x0000000F
#define DBIc_TRACE_FLAGS_MASK   0xFFFFFF00
#define DBIc_TRACE_SETTINGS(imp) (DBIc_DBISTATE(imp)->debug)
#define DBIc_TRACE_LEVEL(imp)   (DBIc_TRACE_SETTINGS(imp) & DBIc_TRACE_LEVEL_MASK)
#define DBIc_TRACE_FLAGS(imp)   (DBIc_TRACE_SETTINGS(imp) & DBIc_TRACE_FLAGS_MASK)
/* DBIc_TRACE_MATCHES(this, crnt): true if this 'matches' (is within) crnt
   DBIc_TRACE_MATCHES(foo, DBIc_TRACE_SETTINGS(imp))
*/
#define DBIc_TRACE_MATCHES(this, crnt)  \
        (  ((crnt & DBIc_TRACE_LEVEL_MASK) >= (this & DBIc_TRACE_LEVEL_MASK)) \
        || ((crnt & DBIc_TRACE_FLAGS_MASK)  & (this & DBIc_TRACE_FLAGS_MASK)) )
/* DBIc_TRACE: true if flags match & DBI level>=flaglevel, or if DBI level>level
   This is the main trace testing macro to be used by drivers.
   (Drivers should define their own DBDtf_* macros for the top 8 bits: 0xFF000000)
   DBIc_TRACE(imp,         0, 0, 4) = if level >= 4
   DBIc_TRACE(imp, DBDtf_FOO, 2, 4) = if tracing DBDtf_FOO & level>=2 or level>=4
   DBIc_TRACE(imp, DBDtf_FOO, 2, 0) = as above but never trace just due to level
*/
#define DBIc_TRACE(imp, flags, flaglevel, level)        \
        (  (flags && (DBIc_TRACE_FLAGS(imp) & flags) && (DBIc_TRACE_LEVEL(imp) >= flaglevel)) \
        || (level && DBIc_TRACE_LEVEL(imp) >= level) )

Patches to DBI::DBD very welcome.

Tim.